The reuse of disposable artificial kidneys has grown greatly in the United States to the extent that reuse is reported to be practiced by more than 75% of all hemodialysis facilities. Reuse requires a cleaning and disinfecting program between uses for the dialyzer, blood and dialysate tubing sets, and related apparatus that guarantees bacteriological safety, the avoidance of contamination by the chemicals used in the cleaning and disinfecting process, and maintenance of the transfer efficiency of the dialyzer membrane. Economic concerns dictate that the reuse cycle be expedited and involve as little expense as possible.
In the past, various reuse procedures and apparatus have been developed to substantially automate cleaning, rinsing and sterilization cycles. U.S. Pat. No. 4,695,385 discloses a reuse system which has enjoyed some success. In this system as normally practiced, sterilization is accomplished by use of a formaldehyde solution, and it is essential that the blood, tubing and blood side of the dialyzer be absolutely free of formaldehyde before reuse since formaldehyde is extremely toxic if permitted to enter a patient's blood stream.
In U.S. Pat. No. 4,695,385, the blood tubing is isolated during the disinfecting cycle with the blood side of the dialyzer in a closed loop filled with the formaldehyde solution. This status is maintained during idle periods of the dialysis machine. To remove the formaldehyde from the system in preparation for another patient, the blood pump is started to circulate the formaldehyde solution in the closed loop, and the dialysate pump is started to circulate dialysate through the dialysate side of the dialyzer. As a result, molecular transfer of the formaldehyde across the dialyzer membrane occurs and the transferred formaldehyde is disposed of with the circulating dialysate. The formaldehyde solution in the blood tubing can be provided with a colored dye indicator so that there can be visual confirmation that the formaldehyde has been substantially removed. Then a chemical test is performed to verify that no disinfectant residue remains in the dialysis system.
A survey in 1996 indicated that about 90% of dialyzer centers used formaldehyde or Renalin as a dialyzer disinfectant. Renalin (Renal Systems, Minneapolis, Minn.) is a hydrogen peroxide-paracetic acid based product. At least one major manufacturer of hemodialysis machines advises that such peracetic acid products should be rinsed out after acting for 20 minutes and warns that they should not be left in the machine overnight because damage to internal components may occur. Also, some studies have indicated increased health risk concerns when peracetic acid is used in reprocessing dialyzers. Thus, heretofore, formaldehyde has been considered preferable for use as a dialyzer disinfectant for the blood circuit components, particularly when the dialysis machine may be idle for several hours, and therefore, preferably should have its blood circuit components exposed to disinfectant while idle to avoid the possibility of bacterial growth.
From the foregoing discussion it is seen that although it has been recognized that ideally the disinfecting agent for disinfecting a hemodyalisis system for reuse should be a chemically pure, non-toxic substance that can be easily removed from the dialyzer so as to minimize the risk to the patient from exposure to trace amounts, heretofore, not only was a suitable non-toxic disinfecting substance never found, but it has been considered that disinfectant removal from the blood side of the system requires that the disinfecting solution be dialyzed for removal of the disinfectant.